Science fiction has a history and an unfortunately well-deserved reputation for sometimes playing fast and loose with the science it uses, often verging into the use of “pure fecking magic” (PFM) in some subgenres.
I classify such technological magic along a spectrum between Wonders and Magic wands.
Wonders are often not explained, and are often best not explained. They have the virtue of being both more consistent in principle with the best currently-known real science and so seeming less contrived.
Magic wands are those plot elements that are allegedly scientific, but suffer from being poorly or overly explained. Not only this, but they suffer from a profound disconnect with actual science, often contradicting fundamental scientific laws.
It is my view that the best SF is that which uses the best science of the time it is written, as it takes more imagination and creativity to write skillfully while working within a set of constraints than to just make shit up, piling up contrived detail upon contrived detail and expect uncritical suspension of disbelief from the readers.
Forcing yourself to write within limits tests your skill as a writer.
The best SF uses good science to aid in the storytelling, lending plausibility to the narrative, not as an impediment, and does not try acts of logical terrorism that would make William of Ockham spin in his grave at a radial velocity of c in the famous equation E=mc^2.
My reasoning for this is that too much profligate magic, too much contrivance and poor explanation overstimulates and desensitizes the imagination, dulling it, even the writer’s own, both distracting and detracting from an otherwise good story.
Even if a plot element does do something fantastical, it should at least be somewhat friendly with the best known science, or do what it does without blatantly violating what we have good reason to think we know.
A good example of that is psionics in the science fiction RPG Traveller. Let’s look at psionic teleportation.
Teleportation is limited in that it must obey the laws of thermodynamics and the conservation of momentum, with limits put on both altitude teleported to and distance travelled on a moving and rotating body like a planet.
Sudden altitude shifts can result in differences in gravitational potential energy which can lead to dangerous overheating or hypothermia. All that energy you pick up or lose has to go somewhere. it gets turned into heat, and transferred to you or bled out of you and dispersed into the universe.
Teleporting from a moving body to a relatively unmoving one is dangerous when travelling great distances even without altitude shifts. It’s smarter and safer to make a series of many very short jumps than one very great one. You keep whatever relative velocity you start with, and this can result in severe injury, or winding up inside a solid object if you jump too far or can’t accurately visualize the target location.
These do more than just make sense. They are plausible ways of providing setting balance and force the psionic player to think about his powers, rather than thinking with his powers.
That can make all the difference between SF and science fantasy or superhero fiction.